F. Meseguer

Electronic structure of modulation n-doped multiple quantum well

Abstract Here we present the differences and similarities in the electronic properties of thick modulation n-doped multiple quantum wells (QW) depending on their symmetry. The study has been done by self-consistent calculations as well as light scattering experiments.

Double Raman Resonances in Semiconductor Multiquantum Wells Induced by High Magnetic Fields

Raman resonance profiles have been measured in GaAs/AlAs multiple-quantum wells (MQW) under magnetic fields up to 20T both for (100) and (111) crystal orientations. The intensity of the resonance increases by several orders of magnitude when the energy difference between two magneto-exciton states, acting as incoming and outgoing channels, respectively, equals the GaAs LO phonon frequency. The results are interpreted as double Raman resonances involving both light-hole (Ln) and heavy-hole (Hn) magnetoexcitons as intermediate states in the scattering process. Double resonances have been observed at precise values of the magnetic field and excitation wavelength for different polarization configurations in both crystal orientations. Our results strongly suggest that the intermediate states in the Raman process are excitons rather than decoupled electrons and/or holes.

Hot Exciton Luminescence in Quantum Wells as a Spectroscopic Tool

Hot carrier effects are the subject of much interest in the study of transport properties in semiconductor heterostructures because of their importance in device reliability. The present work is devoted to some aspects of their optical behaviour. Apart from the intrinsic interest of light emission from hot levels, this phenomenon may reveal new information on the electronic structure and be used as a powerful instrument from the spectroscopic point of view. Advantages of this technique arise from the state of non equilibrium of the recombining carriers which lead to clearer selection rules and, eventually cast new light on the phonon-exciton interaction.

Tunneling time of electrons in modulation n- doped GaAlAsGaAsAlAs quantum wells

Abstract Time resolved luminescence experiments performed on modulation n-doped GaAs Quantum Wells show a non-radiative process associated with the GaAsue5f8AlAs interface. Transfer of charge from GaAs (Γ point) to the AlAs (X point) is proposed as a mechanism to shorten the lifetime of the luminescence process. This process is consistent with magneto-optical experiments and selfconsistent calculations.

Raman Scattering Study of CdTe/CdMnTe Superlattices

Resonant Raman scattering (RRS) by LO phonons is an optical method which provides information on the relationship between lattice-dynamical and electronic properties of crystals. A resonant enhancement of the Raman-scattering efficiency is obtained whenever the energy of the incident photon (incoming channel) or the energy of the scattered photon (outgoing channel) approaches a singularity in the combined density of states of electronic interband transitions. Detailed information is obtained about the electron-phonon interactions, band structure parameters and optical deformation potentials.

Magnetoluminescence studies of modulation n-doped GaAsAlGaAs multiple quantum wells

Abstract In this work we have performed self-consistent calculations of the electronic transitions responsible for the luminescence spectra as a function of the magnetic field in wide quantum wells (QW). We have considered two cases: (a) QWs in which the free electron charge density is held constant and (b) QWs with the Fermi level pinned at the donor level, so as charge transfer is allowed. Both models explain the step-like behaviour of the magnetoluminescence (ML) experiments shown here as well as other ones reported in the literature for this kind of systems. From our results we conclude that the charge transfer only introduces minor differences in the effects under study.